This application claims the benefit of Korean Patent Application No. 2000-86964, filed on Dec. 30, 2000, which is hereby incorporated by reference as if fully set forth herein.
1. Field of the Invention
This invention relates to a method of fabricating a liquid crystal display, and more particularly to a method of fabricating a ferroelectric liquid crystal display that is capable of preventing inadequate injection of a liquid crystal.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) includes a plurality of liquid crystal cells arranged in a matrix. Each liquid crystal cell changes a liquid crystal alignment state in accordance with an applied electric field to control the transmittance of light, thereby providing a gray scale.
A ferroelectric liquid crystal, among other liquid crystals utilized in liquid crystal displays, has the fastest response speed on the order of many microseconds (xe2x96xa1s) to a few milliseconds (ms), because ferroelectric liquid crystal material can polarize in the absence of an applied electric field. In addition, ferroelectric liquid crystal material can provide a wide viewing angle, for use in In-Plane Switching(IPS), without any special electrode structure or alignment film. Accordingly, the ferroelectric liquid crystal is capable of producing a motion picture display represented in a liquid crystal TV.
Generally, as temperature of the ferroelectric liquid crystal decreases, the liquid crystal exhibits a phase-transition process as follows:
Isotropic Phasexe2x86x92Chiral nematic(N*)phasexe2x86x92Smectic C*(Sm C*)Phasexe2x86x92Crystal.
In such a phase-transition process, a ferroelectric liquid crystal display utilizes the smectic phase, which is a ferroelectric liquid crystal phase that exists at a normal (i.e. room) temperature.
The ferroelectric liquid crystal in the smectic phase is provided by injecting and cooling the liquid crystal, which exhibits the isotropic phase or nematic phase. A problem related to inadequate injection occurs because the volume of the liquid crystal decreases upon its phase-transition to the smectic phase.
FIG. 1 is a figure briefly illustrating a liquid crystal injection device for injecting the liquid crystal into a liquid crystal panel.
The liquid crystal injection device in FIG. 1 includes a chamber 12 and a liquid crystal tray 16 which is located within the chamber and connected with an injection hole 14 of a liquid crystal panel 10. Also, the liquid crystal injection device outside of the chamber 12 further includes a heater (not shown) for heating and controlling the temperature of the liquid crystal panel 10 and the liquid crystal tray 16, and a pressure controller (not shown) controlling the inner pressure of the chamber 12. The transition process of the liquid crystal to the desired ferroelectric liquid crystal phase using the aforementioned liquid crystal injection device is as follows.
Firstly, in an exhaust process using the pressure controller, a vacuum state, that is, a state of an equal pressure, is created inside of the chamber 12 and the liquid crystal panel 10. Afterwards, the injection hole 14 of the liquid crystal panel then contacts the liquid crystal tray 16. At the same time, because the liquid crystal panel 10 and the chamber 12 remain in the vacuum state, the liquid crystal in the liquid crystal tray 16 is not injected into the liquid crystal panel 10. Subsequently, N2 gas is injected into the chamber 12 using the pressure controller to make the inner pressure of the chamber 12 higher than the inner pressure of the liquid crystal panel 10. Due to such an inner pressure difference between the chamber 12 and the liquid crystal panel 10, the liquid crystal in the liquid crystal tray 16 is injected into the liquid crystal panel 10 through the injection hole 14. The difference in inner pressure between the chamber 12 and the liquid crystal panel 10 is increased, thereby easily injecting the liquid crystal into the liquid crystal panel 10. At the same time, the liquid crystal panel 10 and the liquid crystal tray 16 both sustain a high temperature, that is, sustain a liquid crystal injection temperature.
Next, the liquid crystal injected into the liquid crystal panel 10 and the liquid crystal panel 10 are cooled down under a certain pressure to make the liquid crystal undergo a phase transition from the isotropic phase or nematic phase to the smectic phase, which is a ferroelectric liquid crystal phase. Accordingly, the liquid crystal injected into the liquid crystal panel 10 experiences a volume decrease of around 3% upon its phase-transition to the smectic phase. As a result of this volumetric decrease, a problem related to inadequate injection of the liquid crystal occurs and a band configured perpendicular to the direction of the liquid crystal injection is formed where liquid crystal material is not injected.
Accordingly, the present invention is directed to a method of fabricating ferroelectric liquid crystal display that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Accordingly, it is an advantage of the present invention to provide a method of fabricating a ferroelectric liquid crystal display that is capable of avoiding problems related to inadequate injection such as a decrease in volume of a cooled injected liquid crystal.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
In order to achieve these and other advantages of the invention, a method of fabricating the ferroelectric liquid crystal display according to one aspect of the present invention, comprises sustaining a pressure in a liquid crystal injected chamber at a first pressure while, at the same time, sustaining the temperature of a liquid crystal panel and a liquid crystal tray contacted to an injection hole thereof at a first temperature to inject the liquid crystal from the liquid crystal tray to the liquid crystal panel; increasing an inner pressure of the chamber to a second pressure higher than the first pressure; and cooling down the liquid crystal panel and the chamber while sustaining the second pressure, and at the same time, maintaining the liquid crystal tray at the first temperature, thereby injecting the liquid crystal into a conventionally and previously un-injected portion of the liquid crystal panel.
The method, according to another aspect of the invention, further comprising the step of, after the step of cooling the liquid crystal panel, decreasing the pressure of the chamber to a third pressure lower than the first pressure, and at the same time, cooling the liquid crystal tray down to a normal temperature.
Here, the first temperature is the temperature where the liquid crystal exhibits one liquid crystal phase comprising one of an isotropic phase and a nematic phase, and the liquid crystal panel is cooled down to the temperature where the injected liquid crystal exhibits the smectic phase.
A method of fabricating a ferroelectric liquid crystal display according to another aspect of the present invention comprises maintaining a pressure in a liquid crystal injected chamber at a first pressure, at the same time, maintaining the temperature of a liquid crystal panel and a liquid crystal tray contacted to an injection hole thereof at a first temperature, to inject the liquid crystal from the liquid crystal tray to the liquid crystal panel; slowly increasing the pressure of the chamber to a second pressure higher than the first pressure while cooling the liquid crystal panel, and at the same time, maintaining the liquid crystal tray at the first temperature to additionally inject the liquid crystal to a previously un-injected portion of the liquid crystal panel.
The method according to another aspect of the invention, firer comprising, after cooling the liquid crystal panel, decreasing the pressure of the chamber to a third pressure lower than the first pressure, and at the same time, cooling the liquid crystal tray to a normal temperature.
The pressure in the chamber is increased from the first pressure to the second pressure corresponding to the cooling temperature of the liquid crystal panel or the pressure of the chamber is increased from the first pressure to the second pressure in step type fashion.
Presently, the first temperature is the temperature where the liquid crystal exhibits one liquid crystal phase comprising one of an isotropic phase and a nematic phase, and the liquid crystal panel is cooled to the temperature where the injected liquid crystal exhibits the smectic phase.
A method of fabricating a ferroelectric liquid crystal display according to the other aspect of the present invention comprises maintaining a pressure in a liquid crystal injected chamber at a first pressure, at the same time, maintaining the temperature of a liquid crystal panel and a liquid crystal tray contacted to an injection hole thereof at a first temperature, to inject the liquid crystal from the liquid crystal tray to the liquid crystal panel; cooling the liquid crystal panel, and during its cooling period, repeatedly changing the pressure of the chamber from the first pressure to a second pressure, higher than the first pressure, and at the same time, maintaining the liquid crystal tray at the first temperature to inject the liquid crystal to a previously un-injected portion of the liquid crystal panel.
The method, according to another aspect of the invention, further comprises, after the step of cooling the liquid crystal panel, decreasing the pressure of the chamber decreased to a third pressure lower than the first pressure, and at the same time, cooling the liquid crystal tray to a normal temperature.
The pressure in the chamber is changed to repeat the cycle of rise-hold to the second pressure and drop-hold to the first pressure.
Here, the first temperature is the temperature where the liquid crystal exhibits one liquid crystal phase comprising one of an isotropic phase and a nematic phase, and the liquid crystal panel is cooled to the temperature where the injected liquid crystal exhibits the smectic phase.